Toner production method and polymer

ABSTRACT

A toner production method including: a melt-kneading step of melt-kneading a resin composition including a binder resin, a colorant, a wax, and a wax dispersant to obtain a melt-kneaded product; and a pulverizing step of pulverizing the melt-kneaded product. Where the temperature of the melt-kneaded product at the end of the melt-kneading step is Tk (° C.), and the softening point of the wax dispersant is Tm (° C.), the relationship of −18≤[Tk−Tm]≤10 is satisfied. The wax dispersant is a polymer in which a styrene acrylic polymer is graft-polymerized to a polyolefin. The styrene acrylic polymer has a monomer unit derived from α-methylstyrene and a monomer unit derived from a cycloalkyl (meth)acrylate.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a toner production method and a polymersuitable for an electrophotographic method, an electrostatic recordingmethod, an electrostatic printing method, a toner jet method, and thelike.

Description of the Related Art

In recent years, electrophotographic full-color copying machines havebecome widespread and have also started finding application to aprinting market. In the printing market, high speed, high image quality,and high productivity are becoming required while adopting to a widerange of media (types of paper).

For example, the copying machines need to have a constant mediavelocity, that is, the ability to continue printing without changing theprocess speed or the set temperature of heating in a fixing deviceaccording to the type of paper even if the type of paper is changed fromthick paper to thin paper. From the viewpoint of constant mediavelocity, it is required that fixing of a toner be properly completed ina wide range of fixing temperature from low temperature to hightemperature.

In order to fix the toner in a wide range of temperature, a method isused in which wax is included in the toner to impart releasability tothe toner. In this case, it is desirable that the dispersion state ofthe wax in the toner be fine and uniform because the properties of thetoner are greatly influenced thereby.

Japanese Patent Application Publication No. 2011-013548 suggests atechnique of including a wax dispersant in a toner to control thedispersion state of the wax in the toner.

Further, Japanese Patent Application Publication No. 2007-264349 alsosuggests to improve the dispersibility of a wax and suppress imagedeterioration by using a toner binder composed of a high-viscosityresin, a low-viscosity resin, and a dispersant.

However, even when the dispersion state of the wax in the toner iscontrolled, where the toner is allowed to stand in a high-temperatureand high-humidity environment, the wax elutes to the toner surface andthe flowability of the toner is lowered. As a result, chargingperformance may be degraded.

Further, in high-speed machines that are adapted for the printingmarket, low-temperature fixability is still insufficient and blockingmay occur when the toner is allowed to stand at a high temperature. Inaddition, since the toner shape is not controlled, the transferefficiency may be insufficient.

Meanwhile, Japanese Patent Application Publication No. 2013-015830suggests to control the shape of the toner by heat treatment and lowerthe adhesive force of the toner in order to enhance the transferefficiency.

SUMMARY OF THE INVENTION

It is known that, in heat-treated toner, the shape of the toner iscontrolled, but wax with high adhesivity elutes close to the tonersurface. Therefore, the flowability of the toner is lowered due to theinfluence of the wax eluted close to the toner surface, and chargingperformance may be lowered.

As described above, there is still room for study aimed at controllingthe dispersion state of the wax in the toner and satisfying all of thecharging performance, low-temperature fixability, and blockingresistance.

In addition, as described above, with a toner using a polyester resin asthe main binder, the charging performance or the charge are sometimesmore difficult to maintain under a high-temperature and high-humidityenvironment than with a toner using a styrene acrylic main binder. Whenthe charging performance varies, the tinge tends to fluctuate duringimage output. This is apparently because moisture is easily adsorbed atthe ester bond portion or terminal portion of the polyester resin, andelectric charges are dissipated through the adsorbed moisture.

Further, in order to attain high image quality, it is necessary toimprove colorant dispersibility. In the toner obtained through themanufacturing method including a melt-kneading step and a pulverizingstep, colorant dispersibility can be improved by lowering thetemperature during melt-kneading, but a wax dispersant with a highmelting point does not melt at a low temperature and wax dispersibilitycannot be improved.

The present invention provides a toner production method that solves theabove problems.

Specifically, the present invention provides a toner production methodcapable of satisfying low-temperature fixability, hot offset resistance,and blocking resistance by controlling the dispersion state of the waxin the toner.

The present invention also provides a toner production method thatenables the demonstration of sufficient charging performance under ahigh-temperature and high-humidity environment and the improvement ofcolorant dispersibility by exposing a wax dispersant having highhydrophobicity on the toner surface.

The present invention provides

a toner production method having:

a melt-kneading step of melt-kneading a resin composition including abinder resin, a colorant, a wax, and a wax dispersant to obtain amelt-kneaded product; and

a pulverizing step of pulverizing the melt-kneaded product, wherein

where a temperature of the melt-kneaded product at an end of themelt-kneading step is Tk (° C.), and

a softening point of the wax dispersant is Tm (° C.),

the Tk and the Tm satisfy the relationship of the following formula (1);and

the wax dispersant is a polymer in which a styrene acrylic polymer isgraft-polymerized to a polyolefin; and moreover

the styrene acrylic polymer has a monomer unit derived fromα-methylstyrene and a monomer unit derived from a cycloalkyl(meth)acrylate:−18≤[Tk−Tm]≤10  formula (1).

Further, the present invention also provides

a polymer in which a styrene acrylic polymer is graft-polymerized to apolyolefin, wherein

the styrene acrylic polymer has a monomer unit derived fromα-methylstyrene and a monomer unit derived from a cycloalkyl(meth)acrylate.

According to the present invention, a toner production method can beprovided that enables the demonstration of sufficient chargingperformance under a high-temperature and high-humidity environment andthe improvement of colorant dispersibility, while satisfyinglow-temperature fixability, hot offset resistance, and blockingresistance.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE is a schematic diagram of a heat treatment apparatus.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawing.

DESCRIPTION OF THE EMBODIMENTS

The toner production method of the present invention has

a melt-kneading step of melt-kneading a resin composition including abinder resin, a colorant, a wax, and a wax dispersant to obtain amelt-kneaded product; and

a pulverizing step of pulverizing the melt-kneaded product, wherein

where a temperature of the melt-kneaded product at an end of themelt-kneading step is Tk (° C.), and

a softening point of the wax dispersant is Tm (° C.),

the Tk and the Tm satisfy the relationship of the following formula (1);and

the wax dispersant is a polymer in which a styrene acrylic polymer isgraft-polymerized to a polyolefin; and moreover

the styrene acrylic polymer has a monomer unit derived fromα-methylstyrene and a monomer unit derived from a cycloalkyl(meth)acrylate:−18≤[Tk−Tm]≤10  formula (1).

In the present invention, the expression “at least XX and not more thanYY” or “XX to YY” representing the numerical range means a numericalrange including a lower limit and an upper limit which are endpoints,unless specified otherwise.

The wax dispersant is a polymer in which a styrene acrylic polymer isgraft-polymerized to a polyolefin. The styrene acrylic polymer hasaffinity for the binder resin in the toner, and the polyolefin hasaffinity for the wax in the toner.

For this reason, domains of wax and wax dispersant are formed in thetoner, and the wax can be finely dispersed. As a result, low-temperaturefixability, hot offset resistance, and blocking resistance can besatisfied.

Further, since the styrene acrylic polymer has a monomer unit derivedfrom a cycloalkyl (meth)acrylate, the wax is finely dispersed in thetoner and at the same time the charging performance can be maintainedeven when the toner is allowed to stand in a high-temperature andhigh-humidity environment.

The term “monomer unit” refers to a form in which a monomer substance ina polymer or resin has reacted.

As a result of the investigation conducted by the inventors of thepresent invention, the following mechanism is presumed.

When a toner is produced by the melt-kneading method, cracking is likelyto occur at the interface with the wax in the pulverizing step, and thewax is likely to be exposed on the toner surface.

It can be presumed that the wax dispersant forming the domain structurewith the wax is also likely to be exposed on the toner surface at thistime.

Meanwhile, it is conceivable that since the wax dispersant, that is, apolymer in which a styrene acrylic polymer is graft-polymerized to apolyolefin (hereinafter also referred to simply as a polymer), has ahydrophobic cycloalkyl group, the adsorption of moisture is more likelyto be inhibited than with the conventional wax dispersant.

Thus, it is conceivable that, as a result of exposing a large amount ofwax dispersant, which is likely to inhibit the adsorption of moisture,on the toner surface, the reduction of the charge amount of the toner bymoisture adsorption is suppressed and the charging performance under ahigh-temperature and high-humidity environment is improved.

Meanwhile, when a cycloalkyl group is introduced into the waxdispersant, the softening point of the wax dispersant increases, but inthe case, for example, where the kneading temperature duringmelt-kneading is set low so as to improve the dispersibility of thecolorant, the wax dispersant is not softened and wax dispersibility issometimes degraded.

Therefore, further investigation has been conducted, and it was foundthat the softening point of the wax dispersant can be lowered even in astate having a hydrophobic cycloalkyl group by including a monomer unitderived from α-methylstyrene as a constituent component of the styreneacrylic polymer.

As a result, it became possible to satisfy all of the hydrophobicity ofthe toner surface, and wax dispersibility and colorant dispersibility inthe toner.

As a result of the investigation conducted by the inventors of thepresent invention, the following mechanism is presumed.

It is conceivable that because the styrene acrylic polymer contains amonomer unit derived from α-methylstyrene, depolymerization ofα-methylstyrene can be used during the synthesis of the polymer, and themolecular weight is prevented from becoming excessively high.

For this reason, the molecular weight of the polymer can be kept low,and the softening point of the wax dispersant can be lowered. Meanwhile,since the cycloalkyl group is present, it is possible to improve thehydrophobicity.

In the present invention, where the temperature of the melt-kneadedproduct at the end of the melt-kneading step (hereinafter also referredto as the outlet temperature of the kneaded product) is Tk (° C.), andthe softening point of the wax dispersant is Tm (° C.), the Tk and theTm satisfy the relationship of the following formula (1). It is alsopreferable that the relationship of the following formula (1)′ besatisfied.−18≤[Tk−Tm]≤10  formula (1)−15≤[Tk−Tm]≤10  formula (1)′

In the present invention, since the softening point of the waxdispersant is controlled to a sufficiently low state, as describedabove, it is possible to control the outlet temperature of the kneadedproduct to an appropriate temperature.

In other words, when the Tk and Tm satisfy the relationship of−18≤[Tk−Tm]≤10, the wax dispersant is appropriately or sufficientlysoftened during melt-kneading of the toner composition, thereby makingcontribution to the fine dispersion of the wax. Furthermore, it ispossible to impart a sufficient shear to the toner composition at thetime of melt-kneading, and the colorant dispersibility can also bemarkedly improved.

More specifically, when [Tk−Tm] is less than −18, the outlet temperatureof the kneaded product is lower than the softening point of the waxdispersant, the wax dispersant is not sufficiently softened during meltkneading of the toner composition, and it is difficult to disperse thewax finely.

Meanwhile, where [Tk−Tm] is larger than 10, the outlet temperature ofthe kneaded product becomes too high when the wax dispersant issufficiently softened. Therefore, sufficient shear cannot be provided tothe toner composition, kneading of the toner composition becomesinsufficient, and wax dispersibility and colorant dispersibility arelowered.

Thus, it is conceivable that both hydrophobicity and colorantdispersibility can be realized by introducing the monomer unit derivedfrom α-methylstyrene into the wax dispersant and decreasing the outlettemperature of the kneaded product during melt kneading.

The polymer of the present invention is a polymer in which a styreneacrylic polymer is graft-polymerized to a polyolefin, wherein thestyrene acrylic polymer has a monomer unit derived from α-methylstyreneand a monomer unit derived from cycloalkyl (meth)acrylate.

In the present invention, the wax dispersant is the polymer.

The polyolefin is not particularly limited, but from the viewpoint ofaffinity for the wax in the toner, the polyolefin may be selected fromwaxes used for the toner described below.

The melting point of the polyolefin is preferably at least 70° C. andnot more than 90° C., and more preferably at least 75° C. and not morethan 85° C.

The polyolefin can be preferably exemplified by a hydrocarbon wax suchas polyethylene, polypropylene, an alkylene copolymer, microcrystallinewax, paraffin wax, and Fischer-Tropsch wax. More preferably, it ispolypropylene having a melting point at least 70° C. and not more than90° C.

In the styrene acrylic polymer, the mass ratio of the polyolefin to thestyrene acrylic polymer is preferably 1:99 to 30:70, and more preferably3:97 to 20:80.

Further, from the viewpoint of reactivity during production of the waxdispersant, it is preferable that the polyolefin have a branchedstructure like polypropylene.

In the present invention, a method for graft polymerizing the styreneacrylic polymer to the polyolefin is not particularly limited, and aconventionally known method can be used.

In the polymer, the styrene acrylic polymer is not particularly limited,provided that it has a monomer unit derived from α-methylstyrene and amonomer unit derived from cycloalkyl (meth)acrylate. Here, cycloalkyl(meth)acrylate means cycloalkyl acrylate or cycloalkyl methacrylate.

By including a monomer unit derived from α-methylstyrene, it is possibleto prevent the molecular weight of the polymer from becoming excessivelyhigh and to keep the softening point of the polymer low.

The amount of the monomer unit derived from α-methylstyrene in thepolymer is preferably at least 5.0% by mass and not more than 30.0% bymass, and more preferably at least 7.0% by mass and not more than 15.0%by mass.

The monomer unit derived from a cycloalkyl (meth)acrylate can berepresented by the following formula (2).

In the formula (2), R₁ represents a hydrogen atom or a methyl group, andR₂ represents a cycloalkyl group.

The R₂ is preferably a cycloalkyl group having at least 3 and not morethan 18 carbon atoms, and more preferably a cycloalkyl group having atleast 4 and not more than 12 carbon atoms.

Specific examples of the cycloalkyl group include a cyclopropyl group, acyclobutyl group, a cyclopentyl group, a cyclohexyl group, at-butylcyclohexyl group, a cycloheptyl group, a cyclooctyl group, etc.

Further, the cycloalkyl group can also have an alkyl group, a halogenatom, a carboxy group, a carbonyl group, a hydroxy group, etc. as asubstituent. The alkyl group is preferably an alkyl group having 1 to 4carbon atoms.

The position and the number of substituents are arbitrary, and when thecycloalkyl group has at least 2 substituents, the substituents may bethe same or different.

Specific examples of the cycloalkyl (meth)acrylate include cyclopropylacrylate, cyclobutyl acrylate, cyclopentyl acrylate, cyclohexylacrylate, cycloheptyl acrylate, cyclooctyl acrylate, cyclopropylmethacrylate, cyclobutyl methacrylate, cyclopentyl methacrylate,cyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctylmethacrylate, dihydrocyclopentadiethyl acrylate, dicyclopentanylacrylate, dicyclopentanyl methacrylate, etc.

Among them, from the viewpoint of hydrophobicity, cyclohexyl acrylate,cycloheptyl acrylate, cyclooctyl acrylate, cyclohexyl methacrylate,cycloheptyl methacrylate, and cyclooctyl methacrylate are preferable.Further, it is more preferable that the monomer unit derived from thecycloalkyl (meth)acrylate be a monomer unit derived from cyclohexylmethacrylate.

The amount of the monomer unit represented by formula (2) in the polymeris preferably at least 1.0% by mass and not more than 40.0% by mass, andmore preferably at least 5.0% by mass and not more than 15.0% by mass.

Examples of monomers other than α-methylstyrene and cycloalkyl(meth)acrylate as constituent components of the styrene acrylic polymerare presented below.

Styrene monomers such as styrene, p-methylstyrene, m-methylstyrene,p-methoxystyrene, p-hydroxystyrene, p-acetoxystyrene, vinyltoluene,ethylstyrene, phenylstyrene, benzylstyrene, etc.; alkyl esters ofunsaturated carboxylic acids (the number of carbon atoms in the alkyl isat least 1 and not more than 18) such as methyl acrylate, ethylacrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate,ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, etc.;vinyl ester monomers such as vinyl acetate, etc.; vinyl ether monomerssuch as vinyl methyl ether; vinyl monomers including a halogen element,such as vinyl chloride; and diene monomers such as butadiene,isobutylene, etc. These monomers can be used singly or in combination oftwo or more kinds.

The amount of the monomer unit derived from the styrene monomer in thepolymer is preferably at least 50.0% by mass and not more than 85.0% bymass, and more preferably at least 60.0% by mass and not more than 80.0%by mass.

Further, from the viewpoint of low-temperature fixability of the toner,it is preferable that the polymer have a monomer unit represented by thefollowing formula (3).

When the polymer has a monomer unit represented by the following formula(3), the glass transition temperature (Tg) of the polymer can belowered. As a result, when the wax dispersant is included in the toner,the charging performance is unlikely to be lowered even when the toneris allowed to stand under a high-temperature and high-humidityenvironment, and the low-temperature fixability is further improved.

The amount of the monomer unit represented by the following formula (3)in the polymer is preferably at least 5.0% by mass and not more than30.0% by mass, more preferably at least 10.0% by mass and not more than20.0% by mass.

In the formula (3), R₃ represents a hydrogen atom or a methyl group, andn represents an integer of at least 1 and not more than 18.

It is more preferable that n be an integer of at least 2 and not morethan 7. When n is an integer of at least 2 and not more than 7, theglass transition temperature (Tg) can be efficiently decreased.

It is preferable that the softening point of the polymer, that is, thesoftening point of the wax dispersant be at least 100.0° C. and not morethan 130.0° C., and more preferably at least 105.0° C. and not more than125.0° C.

The weight average molecular weight (Mw) of the polymer is preferably atleast 5000 and not more than 70,000, and more preferably at least 10,000and not more than 50,000.

When the weight average molecular weight of the polymer is in the aboverange, the movement of the polymer in the toner becomes appropriate. Asa result, the wax dispersibility is further improved, elution of the waxto the toner surface in a high-temperature and high-humidity environmentbecomes appropriate, and the blocking resistance of the toner is furtherimproved.

Further, at the time of fixing and melting, the wax finely dispersed inthe toner can be rapidly transferred to the toner surface, and hotoffset resistance is further improved.

The amount of the polymer is preferably at least 1.0 part by mass andnot more than 10.0 parts by mass, and more preferably at least 2.0 partsby mass and not more than 8.0 parts by mass with respect to 100 parts bymass of the binder resin.

In the case of producing a toner by using the wax dispersant, the binderresin is not particularly limited, but in order to further exert theeffect of the wax dispersant, it is preferable that the binder resininclude an amorphous polyester resin.

The amount of the amorphous polyester resin in the binder resin ispreferably at least 50% by mass, more preferably at least 70% by mass,and even more preferably at least 90% by mass.

The compatibility between the amorphous polyester resin and the wax isinherently poor. Therefore, when wax is added as is to obtain a toner,the wax is present in the segregated state in the toner, and free waxand the like are also generated. As a result, problems such as poorcharging can occur.

However, since the toner includes the wax dispersant, and the binderresin includes the amorphous polyester resin, the dispersion state ofthe wax in the toner can be controlled.

The amorphous polyester resin can be produced according to a usualpolyester synthesis method.

Examples of the monomers suitable for producing the amorphous polyesterresin include polyhydric alcohols (dihydric or trihydric or higheralcohols), polyvalent carboxylic acids (divalent or trivalent or highercarboxylic acids), and acid anhydrides thereof or lower alkyl estersthereof.

Here, in the case of preparing a branched polymer, partial crosslinkingwithin the molecule of the amorphous polyester resin is effective, andfor this purpose, a polyfunctional compound having a valence of three ormore is preferably used. Thus, trivalent or higher carboxylic acids,anhydrides thereof, or lower alkyl esters thereof and/or trihydric orhigher alcohols may be included as monomers.

Examples of the polyhydric alcohols and the polyvalent carboxylic acidssuitable for producing the amorphous polyester resin are presentedhereinbelow.

Examples of dihydric alcohols include ethylene glycol, propylene glycol,1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol,triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol,2-ethyl-1,3-hexanediol, hydrogenated bisphenol A, bisphenols representedby the following formula (A) and derivatives thereof, and diolsrepresented by the following formula (B).

In the formula, R is an ethylene group or a propylene group, and x and yare each an integer of at least 0, the average value of x+y being atleast 0 and not more than 10.

In the formula, R′ is

and x′ and y′ are each an integer of at least 0, the average value ofx′+y′ being at least 0 and not more than 10.)

Examples of divalent carboxylic acids include maleic acid, fumaric acid,citraconic acid, itaconic acid, glutaconic acid, phthalic acid,isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacicacid, azelaic acid, malonic acid, n-dodecenylsuccinic acid,isododecenylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinicacid, n-octenylsuccinic acid, n-octylsuccinic acid, isooctenylsuccinicacid, and isooctylsuccinic acid. Acid anhydrides and lower alkyl estersthereof may also be used.

Among them, maleic acid, fumaric acid, terephthalic acid, adipic acid,and n-dodecenylsuccinic acid are preferably used.

Examples of trihydric or higher alcohols include sorbitol,1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol,tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol,2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane,trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

Among them, glycerol, trimethylolpropane, and pentaerythritol arepreferably used.

Examples of trivalent and higher carboxylic acids include1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid,1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid,1,2,5-hexanetricarboxylic acid,1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane,1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane,1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empol trimeracid. Acid anhydrides and lower alkyl esters thereof may also be used.

Among them, 1,2,4-benzenetricarboxylic acid (trimellitic acid) orderivatives thereof are preferably used because they are inexpensive andthe reaction control can be easily performed.

The dihydric alcohols and the trihydric or higher alcohols can be usedsingly or in combination of a plurality thereof. Likewise, the divalentcarboxylic acids and the trivalent or higher carboxylic acids can beused singly or in combination of a plurality thereof.

The binder resin may be a hybrid resin. For example, the binder resinmay be a hybrid resin of an amorphous polyester resin and a vinyl resinor a vinyl copolymer. In this case, the amount of the amorphouspolyester resin in the hybrid resin is preferably at least 50% by mass,and more preferably at least 70% by mass.

Methods for obtaining a reaction product of a vinyl resin or a vinylcopolymer and an amorphous polyester resin are exemplified by a methodin which a polymerization reaction of one or both resins is performed inthe presence of a polymer including a monomer component reactable withthe vinyl resin (or vinyl copolymer) or the amorphous polyester resin,respectively.

For example, among the monomers constituting amorphous polyester resins,those reactable with the vinyl resins or vinyl copolymers includeunsaturated dicarboxylic acids such as phthalic acid, maleic acid,citraconic acid, itaconic acid and anhydrides thereof.

Among the monomers constituting vinyl resins or the vinyl copolymers,those reactable with amorphous polyester resin components include thosehaving a carboxy group or a hydroxy group, and acrylic acid esters ormethacrylic acid esters.

A resin other than the amorphous polyester resin can also be used as thebinder resin to the extent that the effect of the present invention isnot impaired.

The resin is not particularly limited, and resins used as binder resinsof toners can be used. Examples of such resins include phenolic resins,natural resin-modified phenolic resins, natural resin-modified maleicresins, acrylic resins, methacrylic resins, polyvinyl acetate resins,silicone resins, polyurethane resins, polyamide resins, furan resins,epoxy resins, xylene resins, polyvinyl butyral, terpene resins,coumarone-indene resins, petroleum-based resin, etc.

In the molecular weight distribution measured by gel permeationchromatography (GPC) of tetrahydrofuran (THF) soluble matter of theamorphous polyester resin, the peak molecular weight is preferably atleast 5000 and not more than 13,000. From the viewpoints oflow-temperature fixability and hot offset resistance, it is preferableto satisfy the above range.

Further, the binder resin may include an amorphous polyester resin (L)having a low molecular weight and an amorphous polyester resin (H)having a high molecular weight.

In this case, from the viewpoints of low-temperature fixability and hotoffset resistance, it is preferable that the amount ratio (H/L) of theamorphous polyester resin (H) having a high molecular weight and theamorphous polyester resin (L) having a low molecular weight be at least10/90 and not more than 60/40.

From the viewpoint of hot offset resistance, it is preferable that thepeak molecular weight of the amorphous polyester resin (H) having a highmolecular weight be at least 7000 and not more than 15,000. From theviewpoint of charging performance under a high-temperature andhigh-humidity environment, it is preferable that the acid value of theamorphous polyester resin (H) having a high molecular weight be at least2 mg KOH/g and not more than 20 mg KOH/g.

Meanwhile, from the viewpoint of low-temperature fixability, it ispreferable that the amorphous polyester resin (L) having a low molecularweight have a peak molecular weight of at least 3000 and not more than6000. From the viewpoint of charging performance under ahigh-temperature and high-humidity environment, it is preferable thatthe acid value of the amorphous polyester resin (L) having a lowmolecular weight be not more than 10 mg KOH/g.

The toner of the present invention may include a crystalline resin. Byincluding the crystalline resin, the low-temperature fixability isfurther improved.

Examples of crystalline resins include crystalline ester compounds andcrystalline ether compounds.

By using a crystalline ester compound or a crystalline ether compound,it is possible to plasticize the amorphous polyester resin of the binderresin and further improve the low-temperature fixability. Further, inorder to sufficiently exert the plasticizing effect, it is preferable touse a crystalline polyester resin.

The crystalline polyester resin is obtained, for example, by apolycondensation reaction of a monomer composition including analiphatic diol and an aliphatic dicarboxylic acid as main components.

It is preferable that the crystalline polyester resin be obtained bypolycondensation of an alcohol component including at least one compoundselected from the group consisting of aliphatic diols having at least 2and not more than 22 carbon atoms and derivatives thereof and acarboxylic acid component including at least one compound selected fromthe group consisting of aliphatic dicarboxylic acids having at least 2and not more than 22 carbon atoms and derivatives thereof.

Among them, from the viewpoints of low-temperature fixability andblocking resistance, a crystalline polyester resin is preferred which isobtained by polycondensation of an alcohol component including at leastone compound selected from the group consisting of aliphatic diolshaving at least 6 and not more than 12 carbon atoms and derivativesthereof and a carboxylic acid component including at least one compoundselected from the group consisting of aliphatic dicarboxylic acidshaving at least 6 and not more than 12 carbon atoms and derivativesthereof.

The aliphatic diol is not particularly limited, but it is preferably achain (preferably, linear-chain) aliphatic diol.

Examples of such diols include ethylene glycol, diethylene glycol,triethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropyleneglycol, 1,4-butanediol, 1,4-butadiene glycol, 1,5-pentanediol, neopentylglycol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol,1,10-decanediol, 1,11-undecanediol and 1,12-dodecanediol.

The preferred examples among them include linear-chain aliphaticα,ω-diols such as 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol,1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol and1,12-dodecanediol. Further, the derivatives are not particularlylimited, provided that a similar resin structure can be obtained by thepolycondensation. Examples thereof include derivatives obtained byesterifying the above diols.

In the alcohol component constituting the crystalline polyester resin,at least one compound selected from the group consisting of aliphaticdiols having at least 2 and not more than 22 carbon atoms (preferably atleast 6 and not more than 12 carbon atoms) and derivatives thereof isused in an amount preferably at least 50% by mass, and more preferablyat least 70% by mass with respect to the entire alcohol component.

Polyhydric alcohols other than aliphatic diols can also be used.

Among the polyhydric alcohols, examples of diols other than thealiphatic diols include aromatic alcohols such as polyoxyethylenatedbisphenol A and polyoxypropylenated bisphenol A;1,4-cyclohexanedimethanol, etc.

Examples of trihydric and higher polyhydric alcohols among thepolyhydric alcohols include aromatic alcohols such as1,3,5-trihydroxymethylbenzene, etc.; and aliphatic alcohols such aspentaerythritol, dipentaerythritol, tripentaerythritol,1,2,4-butanetriol, 1,2,5-pentanetriol, glycerin, 2-methylpropanetriol,2-methyl-1,2,4-butanetriol, trimethylolethane, and trimethylolpropane.

Furthermore, monovalent alcohols may be used to such an extent thatproperties of the crystalline polyester resin are not impaired. Examplesof the monohydric alcohols include n-butanol, isobutanol, sec-butanol,n-hexanol, n-octanol, lauryl alcohol, 2-ethylhexanol, decanol,cyclohexanol, benzyl alcohol, dodecyl alcohol, etc.

Meanwhile, the aliphatic dicarboxylic acid is not particularly limited,but it is preferably a chain (preferably linear-chain) aliphaticdicarboxylic acid.

Examples of such aliphatic dicarboxylic acids include oxalic acid,malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,suberic acid, glutaconic acid, azelaic acid, sebacic acid,nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylicacid, dodecanedicarboxylic acid, maleic acid, fumaric acid, mesaconicacid, citraconic acid, and itaconic acid.

Compounds obtained by hydrolyzing anhydrides or lower alkyl esters ofthese acids can be also used. Further, the derivatives are notparticularly limited, provided that a similar resin structure can beobtained by the polycondensation. Examples thereof include derivativesobtained by methylesterification, ethylesterification, or acid chlorideconversion of the dicarboxylic acid components and acid anhydrides ofthe dicarboxylic acid components.

In the carboxylic acid component constituting the crystalline polyesterresin, at least one compound selected from the group consisting ofaliphatic dicarboxylic acids having at least 2 and not more than 22carbon atoms (preferably at least 6 and not more than 12 carbon atoms)and derivatives thereof is used in an amount preferably at least 50% bymass, and more preferably at least 70% by mass with respect to theentire carboxylic acid component.

Polyvalent carboxylic acids other than the aliphatic dicarboxylic acidscan also be used.

Among the polyvalent carboxylic acids, examples of divalent carboxylicacids other than the abovementioned aliphatic dicarboxylic acids includearomatic carboxylic acids such as isophthalic acid, terephthalic acid,etc.; aliphatic carboxylic acids such as n-dodecylsuccinic acid,n-dodecenylsuccinic acid, etc.; and alicyclic carboxylic acids such ascyclohexanedicarboxylic acid, etc. and also acid anhydrides or loweralkyl esters thereof.

Further, among other polyvalent carboxylic acids, examples of trivalentand higher polyvalent carboxylic acids include aromatic carboxylic acidssuch as 1,2,4-benzenetricarboxylic acid (trimellitic acid),2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylicacid, pyromellitic acid, etc., and aliphatic carboxylic acids such as1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid,1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, etc., and alsoderivatives such as lower alkyl esters and acid anhydrides thereof.

A monovalent carboxylic acid may be also included to the extent thatproperties of the crystalline polyester resin are not impaired. Examplesof monovalent carboxylic acids include benzoic acid,naphthalenecarboxylic acid, salicylic acid, 4-methylbenzoic acid,3-methylbenzoic acid, phenoxyacetic acid, biphenylcarboxylic acid,acetic acid, propionic acid, butyric acid, octanoic acid, decanoic acid,dodecanoic acid, stearic acid, etc.

The crystalline polyester resin can be produced according to a usualpolyester synthesis method. For example, a crystalline polyester resincan be obtained by esterifying or transesterifying the carboxylic acidcomponent and the alcohol component and then performing polycondensationby a conventional method under reduced pressure or by introducingnitrogen gas.

The esterification or transesterification reaction can be carried out byusing, as necessary, a usual esterification catalyst or atransesterification catalyst such as sulfuric acid, titanium butoxide,tin 2-ethylhexanoate, dibutyltin oxide, manganese acetate, magnesiumacetate, etc.

Further, the polycondensation reaction may be carried out in thepresence of a usual polymerization catalyst, for example, a well-knowncatalyst such as titanium butoxide, tin 2-ethylhexanoate, dibutyltinoxide, tin acetate, zinc acetate, tin disulfide, antimony trioxide,germanium dioxide, etc. The polymerization temperature and the catalystamount are not particularly limited, and may be determined asappropriate.

In the esterification or transesterification reaction orpolycondensation reaction, in order to increase the strength of theobtained crystalline polyester resin, all the monomers may be loaded atonce, or a method may be used in which a divalent monomer is initiallyreacted in order to reduce the amount of component having a lowmolecular weight and then a trivalent or higher monomer is added andreacted.

The amount of the crystalline polyester resin is preferably at least 1.0part by mass and not more than 15.0 parts by mass, and more preferablyat least 2.0 parts by mass and not more than 10.0 parts by mass withrespect to 100 parts by mass of the binder resin. When the amount of thecrystalline polyester resin is within the abovementioned range, thelow-temperature fixability is improved.

A wax used in the toner production method is not particularly limited,and suitable examples thereof are presented hereinbelow.

Hydrocarbon waxes such as low-molecular-weight polyethylene,low-molecular-weight polypropylene, alkylene copolymers,microcrystalline wax, paraffin wax and Fischer-Tropsch wax; oxides ofhydrocarbon waxes such as oxidized polyethylene wax, or block copolymersthereof; waxes mainly composed of fatty acid esters such as carnaubawax; and waxes obtained by partially or entirely deacidifying fatty acidesters, such as deacidified carnauba wax.

Other examples are presented hereinbelow. Saturated linear-chain fattyacids such as palmitic acid, stearic acid and montanic acid; unsaturatedfatty acids such as brassidic acid, eleostearic acid, and parinaricacid; saturated alcohols such as stearyl alcohol, aralkyl alcohol,behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol;polyhydric alcohols such as sorbitol; esters of fatty acids such aspalmitic acid, stearic acid, behenic acid, and montanic acid withalcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol,carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; fatty acidamides such as linoleic acid amide, oleic acid amide, and lauric acidamide; saturated fatty acid bisamides such as methylene bis-stearic acidamide, ethylene bis-caproic acid amide, ethylene bis-lauric acid amide,and hexamethylene bis-stearic acid amide; unsaturated fatty acid amidessuch as ethylene bis-oleic acid amide, hexamethylene bis-oleic acidamide, N,N′-dioleyladipic acid amide, and N,N′-dioleylsebacic acidamide; aromatic bisamides such as m-xylene bis-stearic acid amide andN,N′-distearylisophthalic acid amide; aliphatic metal salts (generallyreferred to as metal soaps) such as calcium stearate, calcium laurate,zinc stearate, and magnesium stearate; partial esterification productsof fatty acids and polyhydric alcohols such as behenic acidmonoglyceride; and methyl ester compounds having a hydroxyl groupobtained by hydrogenation of vegetable fats and oils.

Among these waxes, from the viewpoint of further improving theinteraction with a wax dispersant, low-temperature fixability, and hotoffset resistance, hydrocarbon waxes such as paraffin waxes andFischer-Tropsch wax, and waxes mainly composed of fatty acid ester waxessuch as carnauba wax are preferable. From the viewpoint of furtherimprovement of the hot offset resistance, hydrocarbon waxes are morepreferable.

The amount of the wax is preferably at least 1.0 part by mass and notmore than 20.0 parts by mass with respect to 100 parts by mass of thebinder resin.

From the viewpoint of achieving both blocking resistance and hot offsetresistance of the toner, it is preferable that the peak temperature ofthe maximum endothermic peak measured using a differential scanningcalorimetry (DSC) device be at least 45° C. and not more than 140° C.,and more preferably at least 70° C. and not more than 100° C.

A colorant used in the toner production method is not particularlylimited, and suitable examples thereof are presented hereinbelow.

Carbon black and colorants obtained by color-matching using a yellowcolorant, a magenta colorant, and a cyan colorant to give a black colorcan be used as the colorants for black toner. A pigment may be usedalone as the colorant, but from the viewpoint of image quality of afull-color image, it is more preferable that a dye and a pigment be usedin combination to improve the sharpness thereof.

Examples of pigments for a magenta toner are presented below. C.I.Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48:2, 48:3, 48:4,49, 50, 51, 52, 53, 54, 55, 57:1, 58, 60, 63, 64, 68, 81:1, 83, 87, 88,89, 90, 112, 114, 122, 123, 146, 147, 150, 163, 184, 202, 206, 207, 209,238, 269, and 282; C.I. Pigment Violet 19; C.I. Vat Red 1, 2, 10, 13,15, 23, 29, and 35.

Examples of dyes for a magenta toner are presented below. C.I. SolventRed 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121; C.I.Disperse Red 9; C.I. Solvent Violet 8, 13, 14, 21, 27; oil-soluble dyessuch as C.I. Disperse Violet 1; and basic dyes such as C.I. Basic Red 1,2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37,38, 39, 40; C.I. Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, and28.

Examples of pigments for a cyan toner are presented below. C.I. PigmentBlue 2, 3, 15:2, 15:3, 15:4, 16, 17; C.I. Vat Blue 6; C.I. Acid Blue 45,and a copper phthalocyanine pigment in which 1 to 5 phthalimidomethylgroups are substituted in the phthalocyanine skeleton.

C.I. Solvent Blue 70 can be used as a dye for a cyan toner.

Examples of pigments for a yellow toner are presented below. C.I.Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23,62, 65, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129,147, 151, 154, 155, 168, 174, 175, 176, 180, 181, and 185; C.I. VatYellow 1, 3, and 20.

C.I. Solvent Yellow 162 can be used as a dye for a yellow toner.

The amount of the colorant is preferably at least 0.1 part by mass andnot more than 30.0 parts by mass with respect to 100 parts by mass ofthe binder resin.

In the toner production method, a charge control agent may be used asnecessary.

A known charge control agent can be used as the charge control agent,but a metal compound of an aromatic carboxylic acid which is colorless,has a high charging speed of the toner, and can stably maintain aconstant charge amount is particularly preferable.

Examples of negative charge control agents include metal compounds ofsalicylic acid, metal compounds of naphthoic acid, metal compounds ofdicarboxylic acid, polymer compounds having sulfonic acid or carboxylicacid in a side chain, polymer compounds having a sulfonic acid salt or asulfonic acid esterification product in a side chain, polymer compoundshaving a carboxylic acid salt or a carboxylic acid esterificationproduct in a side chain, boron compounds, urea compounds, siliconcompounds, and calixarenes.

Examples of positive charge control agents include quaternary ammoniumsalts, polymer compounds having the quaternary ammonium salt in a sidechain, guanidine compounds, and imidazole compounds.

The charge control agent may be added to the toner internally orexternally.

The amount of the charge control agent is preferably at least 0.2 partsby mass and not more than 10.0 parts by mass with respect to 100 partsby mass of the binder resin.

In the toner production method, inorganic fine particles may be used asnecessary.

The inorganic fine particles may be internally added to the toner or maybe mixed with the toner as an external additive.

When the inorganic fine particles are included as an external additive,inorganic fine particles such as silica fine particles, titanium oxidefine particles and aluminum oxide fine particles are preferable.

The inorganic fine particles are preferably hydrophobized with ahydrophobic agent such as a silane compound, silicone oil or a mixturethereof.

When the inorganic fine particles are used for improving the flowabilityof the toner, it is preferable that the inorganic fine particles have aspecific surface area of at least 50 m²/g and not more than 400 m²/g.

Meanwhile, when the inorganic fine particles are used for improving thedurability of the toner, the specific surface area is preferably atleast 10 m²/g and not more than 50 m²/g.

In order to improve the flowability and also stabilize the durability,inorganic fine particles having a specific surface area within the aboveranges may be used in combination.

In the case where the inorganic fine particles are included as anexternal additive, it is preferable that the amount thereof be at least0.1 parts by mass and not more than 10.0 parts by mass with respect to100.0 parts by mass of the toner particles. A publicly known mixer suchas a Henschel mixer may be used for mixing the toner particles and theinorganic fine particles.

The obtained toner can be used as a mono-component developer, but inorder to further improve dot reproducibility and to supply a stableimage for a long period of time, it is preferable that the obtainedtoner be mixed with a magnetic carrier and used as a two-componentdeveloper.

Generally publicly known materials can be used as the magnetic carrier,examples thereof including iron oxide; particles of metals such as iron,lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese,chromium, and rare earth metals, particles of alloys thereof, andparticles of oxides thereof; magnetic bodies such as ferrites; magneticbody dispersed resin carriers (so-called resin carriers) includingmagnetic bodies and a binder resin that holds the magnetic bodies in adispersed state, and the like.

When the toner is mixed with a magnetic carrier and used as atwo-component developer, the mixing ratio of the magnetic carrier andthe toner is preferably such that the toner concentration in thetwo-component type developer is at least 2% by mass and not more than15% by mass, and more preferably at least 4% by mass and not more than13% by mass.

A toner production method includes a melt-kneading step of melt-kneadinga resin composition including a binder resin, a colorant, a wax, and awax dispersant to obtain a melt-kneaded product, and a pulverizing stepof pulverizing the melt-kneaded product.

As a result of toner production through the melt-kneading step, thedispersibility of the wax is improved. In the melt-kneading step, theraw materials of the toner (in particular, the binder resin, the waxdispersant, and the wax) are sufficiently mixed by heat and shear, sothat the dispersibility of the wax in the toner is improved.

As a result of finely dispersing the wax in the toner, elution of thewax to the toner surface under a high-temperature and high-humidityenvironment is reduced and the blocking resistance of the toner isimproved.

In the pulverizing step, the domains of the wax and the wax dispersantare exposed on the toner surface, whereby the hydrophobicity of thetoner is promoted and the charging performance under a high-temperatureand high-humidity environment is improved.

It is also preferable that the production method include a step ofcooling the obtained melt-kneaded product, pulverizing the resultingcooled product, and heat treating the obtained resin particles.

As a result of including the step of heat treating (hereinafter alsoreferred to as a heat treatment step), the charging performance andblocking resistance are further improved as compared with the use of theconventional wax dispersant.

Normally, when a heat treatment step is implemented, since highlyadherent wax is eluted close to the toner surface, the blockingresistance of the toner is lowered and charging defects caused by areduction in flowability of the toner are likely to occur.

However, when the resin particles including the wax dispersant areheat-treated, since the hydrophobic wax dispersant is transferred to thesurface of the resin particles at the same time as the wax, theflowability of the toner does not decrease and the charging performancedoes not decrease even under a high-temperature and high-humidityenvironment. Further, since the wax dispersant has a bulky cycloalkylgroup, the wax is prevented from exuding during the heat treatment stepas compared with the case of using the conventional wax dispersant. Forthis reason, deterioration of blocking resistance of the toner issuppressed.

The toner production method of the present invention will be describedhereinbelow in detail, but this description is not limiting.

First, in a raw material mixing step, prescribed amounts of a binderresin, a colorant, a wax, a wax dispersant and the like are weighed astoner raw materials and blended and mixed to obtain a resin composition(also referred to as a toner composition).

Examples of the apparatuses suitable for the mixing include a Henschelmixer (manufactured by Nippon Coke & Engineering Co., Ltd.); Super Mixer(manufactured by Kawata Mfg Co., Ltd.); Ribocone (manufactured byOkawara Mfg. Co., Ltd.); Nauta mixer, Turbulizer, Cyclomix (HosokawaMicron Corporation); Spiral Pin mixer (manufactured by Pacific Machinery& Engineering Co., Ltd.); and Loedige Mixer (manufactured by MatsuboCorporation).

Next, the obtained resin composition is melt-kneaded to melt the resin,and a colorant, a wax, a wax dispersant and the like are dispersedtherein (melt-kneading step).

Examples of the apparatuses suitable for melt kneading include a TEMtype extruder (manufactured by Toshiba Machine Co., Ltd.); a TEXtwin-screw kneader (manufactured by The Japan Steel Works, Ltd.); a PCMkneader (manufactured by Ikegai Ironworks Corp.); Kneadex (manufacturedby Mitsui Mining Co., Ltd.) and the like. Continuous kneading machinessuch as single-screw or twin-screw extruders are preferred over batchtype kneaders because of suitability thereof for continuous production.

When the temperature of the melt-kneaded product at the end of themelt-kneading step (hereinafter simply referred to as “outlettemperature”) is Tk (° C.) and the softening point of the wax dispersantis Tm (° C.), the Tk and Tm satisfy the relationship of the followingformula (1).−18≤[Tk−Tm]≤10  formula (1)

When the Tk (° C.) and Tm (° C.) satisfy the relationship of the formula(1), as described above, the wax dispersant is appropriately orsufficiently softened when the toner composition is melt-kneaded whichcan contribute to dispersion. Further, since the softening point of thewax dispersant is controlled to be sufficiently low, the outlettemperature of the kneaded product can also be controlled to anappropriate temperature.

From the viewpoints of wax dispersibility and colorant dispersibility,the outlet temperature of the kneaded product is preferably at least100° C. and not more than 130° C., and more preferably at least 105° C.and not more than 125° C.

The obtained melt-kneaded product may be rolled with two rolls or thelike and cooled by water cooling or the like (cooling step).

The obtained cooled material is pulverized to a desired particle size inthe pulverizing step. First, the cooled material is coarsely pulverizedwith a crusher, a hammer mill, a feather mill or the like, and thenfinely pulverized with a Kryptron system (manufactured by Kawasaki HeavyIndustries, Ltd.), Super Rotor (manufactured by Nisshin EngineeringInc.), etc. to obtain resin particles.

The resultant resin particles may be classified into a desired particlesize to obtain toner particles. Examples of devices suitable forclassification include Turboplex, Faculty, TSP, and TTSP (manufacturedby Hosokawa Micron Corporation) and Elbow-Jet (manufactured by NittetsuMining Co., Ltd.).

Further, heat treatment may be performed on the classified resinparticles to obtain toner particles.

Furthermore, when coarse particles are present after the heat treatment,if necessary, a step of removing coarse particles by classification orsieving may be included. Examples of devices suitable for classificationare presented above. Meanwhile, examples of devices suitable for sievinginclude Ultrasonic (manufactured by Koei Sangyo Co., Ltd.), Rezona Sieveand Gyroshifter (manufactured by Tokuju Corporation), Turbo Screener(manufactured by Turbo Kogyo Co., Ltd.), and HI-VOLTA (manufactured byToyo Hitec Co., Ltd.), etc.

Meanwhile, before the heat treatment step, inorganic fine particles orthe like may be added, as necessary, to the obtained resin particles. Asa method for adding inorganic fine particles and the like, predeterminedamounts of resin particles and various known external additives may beblended and then stirred and mixed using a high-speed stirrer that actswith a shearing force on a powder, such as a Henschel mixer and MechanoHybrid (manufactured by Nippon Coke & Engineering Co., Ltd.) and SuperMixer and Nobilta (manufactured by Hosokawa Micron Corporation), as adevice for adding an external additive.

The heat treatment step can be carried out at an arbitrary timing.

A method for carrying out heat treatment on the resin particles by usinga heat treatment apparatus shown in the FIGURE will be specificallydescribed hereinbelow.

The resin particles quantitatively supplied by a raw materialquantitative supply means 1 are guided to an introduction pipe 3installed vertically above a raw material supply means by compressed gasadjusted by a compressed gas flow rate adjustment means 2.

The mixture that has passed through the introduction pipe 3 is uniformlydispersed by a conical projecting member 4 provided in the centralportion of the raw material supply means and is guided to supply pipes 5extending radially in eight directions and then guided to a treatmentchamber 6 where heat treatment is performed.

At this time, the flow of the resin particles supplied to the treatmentchamber 6 is regulated by a regulating means 9 for regulating the flowof the resin particles provided in the treatment chamber 6. Therefore,the resin particles supplied to the treatment chamber 6 are subjected toheat treatment while rotating in the treatment chamber 6, and thencooled.

Hot air for heat treating the supplied resin particles is supplied froma hot air supply means 7, distributed by a distributing member 12, andspirally swirled and introduced into the treatment chamber 6 by aswirling member 13 for swirling hot air. The swirling member 13 forswirling hot air is configured of a plurality of blades, and swirling ofthe hot air can be controlled by the number and angle of the blades (thereference numeral 11 in the FIGURE stands for a hot air supply meansoutlet). The temperature of the hot air supplied into the treatmentchamber 6 is preferably at least 100° C. and not more than 300° C., andmore preferably at least 130° C. and not more than 170° C. at the outletof the hot air supply means 7. When the temperature at the outlet of thehot air supply means 7 is within the above range, it is possible totreat uniformly the particles while preventing fusion and coalescence ofthe particles caused by excessive heating of the resin particles.

Hot air is supplied from the hot air supply means 7. Further, theheat-treated resin particles which have been heat-treated are cooled bycold air supplied from a cold air supply means 8. The temperature of thecold air supplied from the cold air supply means 8 is preferably atleast −20° C. and not more than 30° C. When the temperature of the coolair is within the above range, it is possible to cool efficiently theheat-treated resin particles and prevent fusion and coalescence of theheat-treated resin particles without impeding uniform heat treatment ofthe resin particles. Further, the absolute moisture content of cold airis preferably at least 0.5 g/m³ and not more than 15.0 g/m³.

Next, the cooled heat-treated resin particles are collected by thecollecting means 10 at the lower end of the treatment chamber 6. Ablower (not shown in the FIGURE) is provided at the tip of thecollecting means 10, and the resin particles are sucked and conveyedthereby.

Further, a powder particle supply port 14 is provided so that theswirling direction of the supplied resin particles and the swirlingdirection of the hot air are in the same direction, and the collectingmeans 10 is provided in the tangential direction on the outer peripheralportion of the treatment chamber 6 so as to maintain the swirlingdirection of the swirling resin particles. Furthermore, theconfiguration is such that the cold air supplied from the cold airsupply means 8 is supplied horizontally and tangentially from the outerperipheral portion of the apparatus to the inner peripheral surface ofthe treatment chamber. The swirling direction of the resin particlesbefore the heat treatment which are supplied from the powder particlesupply port 14, the swirling direction of the cold air supplied from thecold air supply means 8, and the swirling direction of the hot airsupplied from the hot air supply means 7 are all the same. Therefore,turbulent flow does not occur in the treatment chamber, the swirlingflow in the apparatus is strengthened, a strong centrifugal force isapplied to the resin particles before the heat treatment, and thedispersibility of the resin particles before the heat treatment isfurther improved. Therefore, heat-treated resin particles having uniformshapes and a small number of coalesced particles can be obtained.

The average circularity of the obtained toner is preferably at least0.960 and not more than 1.000, and more preferably at least 0.965 andnot more than 1.000. When the average circularity of the toner is withinthe above range, the transfer efficiency of the toner is improved.

Methods for measuring various physical properties of the toner and theraw materials will be described hereinbelow.

<Measurement of Peak Temperature of Endothermic Peak of Wax, CrystallineResin, Etc.>

The peak temperature (Tp) of the maximum endothermic peak of the wax,crystalline resin, etc. is measured according to ASTM D 3418-82 by usinga differential scanning calorimeter “Q1000” (manufactured by TAInstruments).

The melting points of indium and zinc are used for temperaturecorrection of the detection unit of the apparatus, and heat of meltingof indium is used for correction of the calorific value.

Specifically, about 5 mg of the sample is accurately weighed and placedin a silver pan to perform one cycle of measurements. An empty silverpan is used as a reference. The measurement conditions are presentedbelow.

Temperature increase rate: 10° C./min.

Measurement start temperature: 20° C.

Measurement end temperature: 180° C.

When the endothermic peak (the endothermic peak derived from the binderresin) does not overlap the endothermic peak of the resin other than thewax and the crystalline resin in the case of using the toner as thesample, the obtained maximum endothermic peak is directly handled asused as the endothermic peak derived from the wax and the crystallineresin.

Meanwhile, in the case of using a toner as a sample, the endothermicpeak of the wax and the endothermic peak of the binder resin can bedistinguished by extracting the wax from the toner by Soxhlet extractionusing a hexane solvent, performing differential scanning calorimetry ofthe isolated wax, and comparing the obtained endothermic peak with theendothermic peak of the toner.

The maximum endothermic peak, as referred to herein, means a peak atwhich the endothermic amount becomes maximum when there is a pluralityof peaks. Also, the peak temperature of the maximum endothermic peak istaken as the melting point.

<Measurement of Weight Average Molecular Weight (Mw), Etc.>

The molecular weight distribution of the wax dispersant and variousresins is measured in the following manner by gel permeationchromatography (GPC).

First, the sample is placed in tetrahydrofuran (THF), allowed to standfor several hours at 25° C., thoroughly shaken, thoroughly mixed withTHF, and allowed to stand for at least 12 hours until there is nocoalescence of the sample.

The sample in this case is allowed to stay in THF for 24 hours.Thereafter, the resultant solution is passed through a sample treatmentfilter (pore size at least 0.2 μm and not more than 0.5 μm, for example,Sample Pretreatment Cartridge H-25-2 (manufactured by TosohCorporation)) and used as a sample for GPC.

Further, the sample concentration is adjusted to be at least 0.5 mg/mLand not more than 5.0 mg/mL. Measurements are performed under thefollowing conditions by using this sample solution.

The column is stabilized in a heat chamber at 40° C., tetrahydrofuran(THF) is allowed to flow as a solvent at a flow rate of 1 mL per minuteinto the column at this temperature, and measurements are performed byinjecting about 100 μL of the sample solution.

A plurality of commercially available polystyrene gel columns iscombined as a column. A combination of shodex GPC KF-801, 802, 803, 804,805, 806, 807, and 800 P manufactured by Showa Denko K.K. or acombination of TSKgel G1000H (H_(XL)), G2000H (H_(XL)), G3000H (H_(XL)),G4000H (H_(XL)), G5000H (H_(XL)), G6000H (H_(XL)), G7000H (H_(XL)) andTSKgurd column manufactured by Tosoh Corporation is used.

In measuring the molecular weight of the sample, the molecular weightdistribution of the sample is calculated from the relationship betweenthe logarithmic value of a calibration curve prepared from severalmonodisperse polystyrene standard samples and the count value.

As a standard polystyrene sample for preparing a calibration curve, asample having a molecular weight of about 1×10² to 1×10⁷ manufactured byTosoh Corporation or Showa Denko K.K. is used, and at least about 10standard polystyrene samples are used. The detector uses an RI(refractive index) detector.

<Measurement of Weight Average Particle Diameter (D4) of Toner>

The weight average particle diameter (D4) of the toner is calculated byusing a precision particle size distribution measuring apparatus“Coulter Counter Multisizer 3” (registered trademark, manufactured byBeckman Coulter, Inc.), which is based on a pore electrical resistancemethod and equipped with a 100 μm aperture tube, and dedicated software“Beckman Coulter Multisizer 3 Version 3.51” (manufactured by BeckmanCoulter, Inc.) provided with the apparatus to set measurement conditionsand analyze measurement data, performing measurements with the number ofeffective measurement channels of 25,000, and analyzing the measurementdata.

An electrolytic aqueous solution used for the measurement is prepared bydissolving special grade sodium chloride in ion-exchanged water to aconcentration of about 1% by mass. For example, “ISOTON II”(manufactured by Beckman Coulter, Inc.) can be used.

The dedicated software is set as follows before the measurements andanalysis.

On the “CHANGE STANDARD MEASUREMENT METHOD (SOM) SCREEN” of thededicated software, the total count number of the control mode is set to50,000 particles, one measurement cycle is performed, and a valueobtained by using “STANDARD PARTICLE 10.0 μm” (manufactured by BeckmanCoulter, Inc.) is set as a Kd value. The threshold and the noise levelare automatically set by pressing the “threshold/noise level measurementbutton”. Further, the current is set to 1600 μA, the gain is set to 2,the electrolytic solution is set to ISOTON II, and “flush aperture tubeafter measurement” is checked.

On the “SCREEN FOR CONVERSION SETTING FROM PULSE TO PARTICLE DIAMETER”of the dedicated software, the bin interval is set to a logarithmicparticle diameter, the particle diameter bin is set to 256 particlediameter bins, and the particle diameter range is set to at least 2 μmand not more than 60 μm.

Specific measurement methods are described below.

(1) Approximately 200 mL of the electrolytic aqueous solution is placedin a 250-mL round-bottom glass beaker specifically designed forMultisizer 3, the beaker is set in the sample stand, and stirring with astirrer rod is performed counterclockwise at 24 rotations/sec. Dirt andair bubbles in the aperture tube are removed by the “FLUSH OF APERTURE”function of the dedicated software.

(2) Approximately 30 mL of the electrolytic aqueous solution is placedin a glass 100-mL flat-bottom beaker. As a dispersant, a dilutedsolution, about 0.3 mL, prepared by diluting “Contaminon N” (10% by massaqueous solution of a neutral detergent of pH 7 for washing precisionmeasuring instruments; composed of a nonionic surfactant, an anionicsurfactant, and an organic builder; manufactured by Wako Pure ChemicalIndustries, Ltd.) by a factor of 3 in terms of mass with ion-exchangedwater is added to the electrolytic aqueous solution.

(3) A predetermined amount of ion-exchanged water is placed in a watertank of an ultrasonic disperser “Ultrasonic Dispersion System Tetora150” (manufactured by Nikkaki Bios Co., Ltd.) with an electrical outputof 120 W in which two oscillators with an oscillation frequency of 50kHz are incorporated with a phase shift of 180 degrees, and about 2 mLof Contaminon N is added into the water tank.

(4) The beaker of (2) is set in a beaker fixing hole of the ultrasonicdisperser, and the ultrasonic disperser is actuated. Then, the heightposition of the beaker is adjusted so that the resonance state of theliquid surface of the electrolytic aqueous solution in the beaker ismaximized.

(5) Approximately 10 mg of the toner is added little by little to theelectrolytic aqueous solution and dispersed while irradiating theelectrolytic aqueous solution in the beaker of (4) with ultrasonicwaves. Then, the ultrasonic dispersion process is further continued for60 seconds. During the ultrasonic dispersion, the water temperature inthe water tank is adjusted as appropriate to at least 10° C. and notmore than 40° C.

(6) The electrolytic aqueous solution of (5) in which the toner has beendispersed is dropwise added using a pipette to the round-bottom beakerof (1) which has been placed in the sample stand, and the measurementconcentration is adjusted to about 5%. Then, measurement is performeduntil the number of particles to be measured reaches 50,000.

(7) The measurement data are analyzed with the dedicated softwareprovided with the apparatus to calculate the weight average particlediameter (D4). The “AVERAGE DIAMETER” on the “ANALYSIS/VOLUMESTATISTICAL VALUE (ARITHMETIC AVERAGE)” screen when set as graph/% byvolume with the dedicated software is the weight average particlediameter (D4).

<Measurement of Average Circularity>

The average circularity of the toner is measured under measurement andanalysis conditions at the time of a calibration operation with a flowparticle image analyzer “FPIA-3000” (manufactured by SysmexCorporation).

A specific measurement method is as described below. First, about 20 mLof ion-exchanged water from which solid impurities and the like havebeen removed in advance is poured into a glass vessel. Then, about 0.2mL of a diluted solution prepared by diluting “Contaminon N”

(10% by mass aqueous solution of a neutral detergent of pH 7 for washingprecision measuring instruments; composed of a nonionic surfactant, ananionic surfactant, and an organic builder; manufactured by Wako PureChemical Industries, Ltd.) by a factor of 3 in terms of mass withion-exchanged water is added as a dispersant to the vessel. Further,about 0.02 g of a measurement sample is added to the vessel, and thedispersion treatment is performed for 2 minutes with the ultrasonicdisperser to obtain a dispersion solution for measurement. At that time,the dispersion solution is appropriately cooled so as to have atemperature of at least 10° C. and not more than 40° C. A desktopultrasonic cleaning and dispersing unit having an oscillatory frequencyof 50 kHz and an electrical output of 150 W (for example, “VS-150”(manufactured by VELVO-CLEAR)) is used as the ultrasonic disperser. Apredetermined amount of ion-exchanged water is poured into a water tank,and about 2 ml of the Contaminon N is added to the water tank.

A flow particle image analyzer equipped with a standard objective lens(magnification: 10) is used in the measurement, and a particle sheath“PSE-900A” (manufactured by Sysmex Corporation) is used as a sheathliquid. The dispersion solution prepared in accordance with theabovementioned procedure is introduced into the flow particle imageanalyzer, and 3000 toner particles are subjected to measurementaccording to the total count mode in the HPF measurement mode. Then, theaverage circularity of the toner is determined with a binarizationthreshold at the time of particle analysis set to 85% and particles tobe analyzed limited to ones with a circle-equivalent diameter of atleast 1.985 μm and not more than 39.69 μm.

<Measurement of Softening Point of Polymer>

The softening point of the polymer is measured using a constant-loadextrusion type capillary rheometer “Flow Characteristic EvaluationDevice: Flow Tester CFT-500D” (manufactured by Shimadzu Corporation)according to the manual attached to the device.

In this device, the temperature of the measurement sample filled in acylinder is raised and the sample is melted while applying a constantload from above the measurement sample with a piston, the meltedmeasurement sample is extruded from a die at the bottom of the cylinder,and a flow curve showing the relationship between the piston descentamount and the temperature at this time can be obtained.

In the present invention, the “melting temperature in a ½ method”described in the manual attached to the “Flow Characteristic EvaluationDevice: Flow Tester CFT-500D” is taken as the softening point. Themelting temperature in the ½ method is calculated as follows. First, ½of the difference between the descent amount Smax of the piston at thetime when the outflow has ended and the descent amount Smin of thepiston at the time when the outflow has started is calculated (this isdenoted by X; X=(Smax−Smin)/2). The temperature at the flow curve whenthe descending amount of the piston at the flow curve is the sum of Xand Smin is the melting temperature in the ½ method.

About 1.0 g of the sample is compression-molded at about 10 MPa by usinga tablet compacting compressor (NT-100H, manufactured by NPa Systems,Inc.) for about 60 seconds in an environment of 25° C. to obtain themeasurement sample of a columnar shape with a diameter of about 8 mm.

Measurement conditions of CFT-500D are as follows.

Test mode: temperature rising method

Starting temperature: 50° C.

Temperature reached: 200° C.

Measurement interval: 1.0° C.

Heating rate: 4.0° C./min

Piston cross section area: 1.000 cm²

Test load (piston load): 10.0 kgf (0.9807 MPa)

Preheating time: 300 seconds

Die hole diameter: 1.0 mm

Die length: 1.0 mm

EXAMPLES

The present invention will be explained hereinbelow in greater detail byexamples thereof. The present invention is not intended to be limited tothe below-described examples. In the examples, number of parts and % areall based on the mass standard, unless specifically stated otherwise.

Production Example of Polymer 1

A total of 300.0 parts of xylene and 10.0 parts of polypropylene (thepeak temperature (melting point) of the maximum endothermic peak at 90°C.) were placed in an autoclave reaction vessel equipped with athermometer and a stirrer, and sufficiently dissolved. After purgingwith nitrogen, a liquid mixture of 63.0 parts of styrene, 10.0 parts ofα-methylstyrene, 5.0 parts of cyclohexyl methacrylate, 12.0 parts ofbutyl acrylate, and 250.0 parts of xylene was added dropwise at 180° C.for 3 hours and polymerization was performed. Further, holding at thistemperature for 30 minutes was followed by the removal of solvent toobtain Polymer 1. Physical properties of the obtained polymer are shownin Table 1. In the table, Mp represents the peak molecular weight, andMw represents the weight average molecular weight.

Production Examples of Polymers 2 to 22

Polymers 2 to 22 were obtained in the same manner as in the productionexample of Polymer 1 except that the conditions in the productionexample of Polymer 1 were appropriately changed as indicated in Table 1.In order to obtain the addition amount of α-methylstyrene shown in Table1, the amount of styrene added was adjusted (adjusted so that the rawmaterial composition of the polymer became 100 parts as a whole).Physical properties of the obtained polymers are shown in Table 1.

TABLE 1 Polyolefin α- Cycloalkyl (meth)acrylate Other compounds Physicalproperties Polymer Melting methylstyrene Type and number of carbon Typeand Softening No. Type point (° C.) (mass %) atoms in alicyclic portionn in Formula (3) point (° C.) Mp Mw 1 Polypropylene 80 10.0 Cyclohexylmethacrylate 6 Butyl acrylate 4 115.0 11000 39000 2 Polypropylene 7510.0 Cyclohexyl methacrylate 6 Butyl acrylate 4 115.0 10500 36000 3Polypropylene 85 10.0 Cyclohexyl methacrylate 6 Butyl acrylate 4 115.011200 41000 4 Polypropylene 80 10.0 Cyclohexyl methacrylate 6 Isobutylacrylate 4 115.0 10000 39000 5 Polypropylene 80 10.0 Cyclohexylmethacrylate 6 2-Ethylhexl acrylate 7 115.0 11000 38000 6 Polypropylene80 10.0 Cyclohexyl methacrylate 6 Ethyl acrylate 2 115.0 10000 37500 7Polypropylene 80 25.0 Cyclohexyl methacrylate 6 Butyl acrylate 4 105.09500 35000 8 Polypropylene 80 7.0 Cyclohexyl methacrylate 6 Butylacrylate 4 125.0 12000 43000 9 Polypropylene 60 10.0 Cyclohexylmethacrylate 6 Butyl acrylate 4 115.0 10500 38000 10 Polypropylene 10010.0 Cyclohexyl methacrylate 6 Butyl acrylate 4 115.0 11000 40000 11Polyethylene 80 10.0 Cyclohexyl methacrylate 6 Butyl acrylate 4 115.010000 35000 12 Polypropylene 80 10.0 Cyclopentyl methacrylate 5 Butylacrylate 4 115.0 10000 37000 13 Polypropylene 80 10.0 Cyclobutylmethacrylate 4 Butyl acrylate 4 115.0 10000 36000 14 Polypropylene 8010.0 Cycloheptyl methacrylate 7 Butyl acrylate 4 115.0 11500 39500 15Polypropylene 80 10.0 Cyclooctyl methacrylate 8 Butyl acrylate 4 115.012000 39500 16 Polypropylene 80 10.0 Cyclohexyl methacrylate 6 — — 115.010000 37500 17 Polypropylene 80 35.0 Cyclohexyl methacrylate 6 Butylacrylate 4 95.0 8500 32000 18 Polypropylene 80 1.0 Cyclohexylmethacrylate 6 Butyl acrylate 4 130.0 12500 43000 19 Polypropylene 8010.0 — — — — 115.0 10000 35000 20 Polypropylene 80 — Cyclohexylmethacrylate 6 — — 135.0 13000 49000 21 Polyethylene 80 10.0 Cyclohexylmethacrylate 6 — — 115.0 11000 39000 22 Polyethylene 80 — — — — — 135.013000 52000

Production Example of Amorphous Polyester Resin (L)

Polyoxypropylene (2.2)-2,2-bis(4- 72.0 parts hydroxyphenyl)propane (0.20mol; 100.0 mol % based on the total number of moles of polyhydricalcohol), terephthalic acid 28.0 parts (0.17 mol; 96.0 mol % based onthe total number of moles of polyvalent carboxylic acid), and tin2-ethylhexanoate (esterification catalyst): 0.5 parts.

The abovementioned materials were weighed into a reaction vesselequipped with a cooling tube, a stirrer, a nitrogen introducing tube,and a thermocouple.

Next, after purging the reaction vessel with nitrogen gas, thetemperature was gradually raised under stirring, and the components werereacted for 4 hours under stirring at a temperature of 200° C.

Further, the pressure inside the reaction vessel was reduced to 8.3 kPaand maintained for 1 hour, followed by cooling to 180° C. and returningto atmospheric pressure.

Trimellitic anhydride 3.0 parts (0.01 mol; 4.0 mol % based on the totalnumber of moles of polyvalent carboxylic acid), and tert-butyl catechol(polymerization inhibitor) 0.1 parts.

Then, the abovementioned materials were added, the pressure inside thereaction vessel was reduced to 8.3 kPa, and the reaction was continuedfor 1 hour while maintaining the temperature at 180° C. After confirmingthat the softening point reached 90° C., the temperature was lowered tostop the reaction and obtain an amorphous polyester resin (L).

The amorphous polyester resin (L) thus obtained had a peak molecularweight (Mp) of 5500 and a softening point (Tm) of 90° C.

Production Example of Amorphous Polyester Resin (H)

Polyoxypropylene (2.2)-2,2-bis(4- 72.3 parts hydroxyphenyl)propane (0.20mol; 100.0 mol % based on the total number of moles of polyhydricalcohol), terephthalic acid 18.3 parts (0.11 mol; 65.0 mol % withrespect to the total number of moles of polyvalent carboxylic acid),fumaric acid 2.9 parts (0.03 mol; 15.0 mol % with respect to the totalnumber of moles of polyvalent carboxylic acid), and tin 2-ethylhexanoate(esterification catalyst) 0.5 parts.

The abovementioned materials were weighed into a reaction vesselequipped with a cooling tube, a stirrer, a nitrogen inlet tube, and athermocouple.

Next, after purging the reaction vessel with nitrogen gas, thetemperature was gradually raised under stirring, and the components werereacted for 2 hours under stirring at a temperature of 200° C.

Further, the pressure inside the reaction vessel was reduced to 8.3 kPaand maintained for 1 hour, followed by cooling to 180° C. and returningto atmospheric pressure.

Trimellitic anhydride 6.5 parts (0.03 mol; 20.0 mol % with respect tothe total number of moles of polyvalent carboxylic acid), and tert-butylcatechol (polymerization inhibitor) 0.1 parts.

Then, the abovementioned materials were added, the pressure inside thereaction vessel was reduced to 8.3 kPa, and the reaction was continuedfor 15 hours while maintaining the temperature at 160° C. Afterconfirming that the softening point reached 137° C., the temperature waslowered to stop the reaction and obtain an amorphous polyester resin(H).

The amorphous polyester resin (H) thus obtained had a peak molecularweight (Mp) of 9000 and a softening point (Tm) of 137° C.

Production Example of Crystalline Polyester Resin (C)

1,6-Hexanediol 34.5 parts (0.29 mol; 100.0 mol % based on the totalnumber of moles of polyhydric alcohol), dodecanedioic acid 65.5 parts(0.28 mol; 100.0 mol % with respect to the total number of moles ofpolyvalent carboxylic acid), and tin 2-ethylhexanoate 0.5 parts.

The abovementioned materials were weighed into a reaction vesselequipped with a cooling tube, a stirrer, a nitrogen inlet tube, and athermocouple.

Next, after purging the reaction vessel with nitrogen gas, thetemperature was gradually raised under stirring, and the components werereacted for 3 hours under stirring at a temperature of 140° C.

Further, the pressure inside the reaction vessel was reduced to 8.3 kPa,and the reaction was conducted for 4 hours while maintaining thetemperature at 200° C.

The interior of the reaction vessel was then depressurized to not morethan 5 kPa and a reaction was conducted or 3 hours at 200° C. to obtaina crystalline polyester resin (C).

Production Example of Toner 1

Amorphous polyester resin (L) 50.0 parts, amorphous polyester resin (H)50.0 parts, crystalline polyester resin (C) 5.0 parts, polymer 1 5.0parts, Fischer-Tropsch wax 5.0 parts (hydrocarbon wax, peak temperatureof the maximum endothermic peak at 90° C.), C.I. Pigment Blue 15:3 7.0parts, and 3,5-di-t-butylsalicylic acid aluminum 0.3 parts compound(Bontron E 88 manufactured by Orient Chemical Industries, Ltd.).

The abovementioned materials were mixed at a rotation speed of 20 s⁻¹and for a rotation time of 5 minutes by using a Henschel mixer (ModelFM-75, manufactured by Mitsui Mining Co., Ltd.), and then melt-kneadedin a twin-screw kneader (PCM-30 type, manufactured by Ikegai Corp). Thebarrel temperature during melt-kneading was set such that the outlettemperature of the melt-kneaded product was 115° C. The outlettemperature of the melt-kneaded product was directly measured using ahandy type thermometer HA-200E manufactured by Anritsu Meter Co., Ltd.

The obtained melt-kneaded product was cooled and coarsely pulverized tonot more than 1 mm with a hammer mill to obtain a coarsely pulverizedproduct. The obtained coarsely pulverized product was finely pulverizedwith a mechanical pulverizer (T-250, manufactured by Turbo Kogyo Co.,Ltd.). Further, classification was carried out using Faculty F-300(manufactured by Hosokawa Micron Corporation) to obtain resin particles.The operating conditions of Faculty F-300 were set as follows:classification rotor rotation speed 130 s⁻¹ and dispersion rotorrotation speed 120 s⁻¹.

Using the obtained resin particles, heat treatment was performed withthe heat treatment apparatus shown in the FIGURE to obtain tonerparticles. The operating conditions were set as follows. Feed rate: 5kg/hr, hot air temperature: 150° C., hot air flow rate: 6 m³/min, coldair temperature: −5° C., cold air flow rate: 4 m³/min, blower airvolume: 20 m³/min, and injection air flow rate: 1 m³/min.

A total of 1.0 part of hydrophobic silica (BET: 200 m²/g) and 1.0 partof fine titanium oxide particles (BET: 80 m²/g) surface-treated withisobutyltrimethoxysilane were mixed with 100 parts of toner particles byusing a Henschel mixer (FM-75 type, manufactured by Mitsui Mining Co.,Ltd.) at a rotation speed of 30 s⁻¹ for a rotation time of 10 minutes toprepare toner 1.

Production Example of Toners 2 to 33

Toners 2 to 33 were obtained by performing the same operations as inProduction Example of Toner 1, except that the conditions wereappropriately changed so that the addition amount of the crystallinepolyester resin (C), the type and addition amount of the polymer, theoutlet temperature, and the heat treatment that were used in ProductionExample of Toner 1 were changed as shown in Table 2. The productionconditions of the toners are shown in Table 2.

TABLE 2 Number of Polymer Outlet added parts of Softening temperaturecrystalline point Number of of kneaded polyester resin (° C.) addedparts product (° C.) Heat Toner No. (parts by mass) Type [Tm] (parts bymass) [Tk] Tk − Tm treatment 1 5.0 Polymer 1 115.0 5.0 115.0 0.0 Yes 25.0 Polymer 1 115.0 2.0 115.0 0.0 Yes 3 5.0 Polymer 1 115.0 8.0 115.00.0 Yes 4 5.0 Polymer 2 115.0 5.0 115.0 0.0 Yes 5 5.0 Polymer 3 115.05.0 115.0 0.0 Yes 6 5.0 Polymer 4 115.0 5.0 115.0 0.0 Yes 7 5.0 Polymer5 115.0 5.0 115.0 0.0 Yes 8 5.0 Polymer 6 115.0 5.0 115.0 0.0 Yes 9 5.0Polymer 7 105.0 5.0 105.0 0.0 Yes 10 5.0 Polymer 8 125.0 5.0 125.0 0.0Yes 11 5.0 Polymer 7 105.0 5.0 115.0 10.0 Yes 12 5.0 Polymer 8 125.0 5.0115.0 −10.0 Yes 13 5.0 Polymer 1 115.0 5.0 110.0 −5.0 Yes 14 5.0 Polymer1 115.0 5.0 125.0 10.0 Yes 15 5.0 Polymer 1 115.0 5.0 115.0 0.0 — 16 —Polymer 1 115.0 5.0 115.0 0.0 Yes 17 5.0 Polymer 1 115.0 0.5 115.0 0.0Yes 18 5.0 Polymer 1 115.0 12.0 115.0 0.0 Yes 19 5.0 Polymer 9 115.0 5.0115.0 0.0 Yes 20 5.0 Polymer 10 115.0 5.0 115.0 0.0 Yes 21 5.0 Polymer11 115.0 5.0 115.0 0.0 Yes 22 5.0 Polymer 12 115.0 5.0 115.0 0.0 Yes 235.0 Polymer 13 115.0 5.0 115.0 0.0 Yes 24 5.0 Polymer 14 115.0 5.0 115.00.0 Yes 25 5.0 Polymer 15 115.0 5.0 115.0 0.0 Yes 26 5.0 Polymer 16115.0 5.0 115.0 0.0 Yes 27 5.0 Polymer 17 95.0 5.0 105.0 10.0 Yes 28 5.0Polymer 18 130.0 5.0 115.0 −15.0 Yes 29 — Polymer 19 115.0 5.0 115.0 0.0— 30 — Polymer 20 135.0 5.0 115.0 −20.0 — 31 — Polymer 21 115.0 5.0 95.0−20.0 — 32 — Polymer 21 115.0 5.0 130.0 15.0 — 33 — Polymer 22 135.0 0.5105.0 −30.0 —

Production Example of Magnetic Core Particle 1

Step 1 (Weighing and Mixing Step):

Fe₂O₃ 62.7 parts, MnCO₃ 29.5 parts, Mg(OH)₂ 6.8 parts, SrCO₃ 1.0 part.

Ferrite raw materials listed hereinabove were weighed to obtain theabovementioned composition ratio. The components were then pulverizedand mixed for 5 hours with a dry vibration mill using stainless steelbeads having a diameter of ⅛ inches.

Step 2 (Pre-Calcination Step):

The pulverized product thus obtained was molded into square pellets witha side of about 1 mm with a roller compactor. The pellets were treatedto remove a coarse powder with a vibrating sieve having an opening of 3mm, then fine powder was removed with a vibration sieve having anopening of 0.5 mm, and then calcination was performed for 4 hours at atemperature of 1000° C. under a nitrogen atmosphere (oxygenconcentration: 0.01% by volume) in a burner type calcination furnace toprepare calcined ferrite. The composition of the obtained calcinedferrite is presented below.(MnO)_(a)(MgO)_(b)(SrO)_(c)(Fe₂O₃)_(d)

In the above formula, a=0.257, b=0.117, c=0.007, and d=0.393

Step 3 (Pulverizing Step):

After pulverization to about 0.3 mm with a crusher, 30 parts of waterwas added to 100 parts of the pre-calcined ferrite, and pulverizationusing ⅛-inch diameter zirconia beads was performed for 1 hour with a wetball mill. The slurry was pulverized with a wet ball mill using aluminabeads having a diameter of 1/16 inches for 4 hours to obtain ferriteslurry (finely pulverized product of pre-calcined ferrite).

Step 4 (Granulation Step):

A total of 1.0 part of ammonium polycarboxylate as a dispersant and 2.0parts of polyvinyl alcohol as a binder were added to the ferrite slurryper 100 parts of the pre-calcined ferrite, followed by granulation intospherical particles with a spray drier (manufacturer: Ohkawara KakohkiCo., Ltd.). The obtained particles were adjusted in particle size andthen heated for 2 hours at 650° C. by using a rotary kiln to removeorganic components of the dispersant and the binder.

Step 5 (Calcination Step):

In order to control the calcination atmosphere, the temperature wasraised over 2 hours from room temperature to a temperature of 1300° C.in a nitrogen atmosphere (oxygen concentration 1.00% by volume) in anelectric furnace, followed by calcination for 4 hours at a temperatureof 1150° C. The temperature was then lowered over 4 hours to 60° C., theatmosphere was returned from the nitrogen atmosphere to that of the air,and the product was taken out at a temperature of not more than 40° C.

Step 6 (Screening Process):

After crushing the agglomerated particles, the products with a lowmagnetic force were cut by magnetic separation and coarse particles wereremoved by sieving with a 250 μm mesh sieve to obtain magnetic coreparticles 1 with a 50% particle diameter (D50), based on a volumedistribution standard, of 37.0 μm.

<Preparation of Coating Resin 1>

Cyclohexyl methacrylate monomer 26.8% by mass, methyl methacrylatemonomer 0.2% by mass, methyl methacrylate macromonomer 8.4% by mass(macromonomer having a methacryloyl group at one end and a weightaverage molecular weight of 5000), toluene 31.3% by mass, methyl ethylketone 31.3% by mass, azobisisobutyronitrile 2.0% by mass.

Of the abovementioned materials, the cyclohexyl methacrylate monomer,methyl methacrylate monomer, methyl methacrylate macromonomer, tolueneand methyl ethyl ketone were placed in a four-necked separable flaskequipped with a reflux condenser, a thermometer, a nitrogen introducingtube, and a stirrer. Nitrogen gas was introduced to obtain a fullynitrogen atmosphere, followed by heating to 80° C. Then,azobisisobutyronitrile was added, followed by refluxing for 5 hours andpolymerization. Hexane was injected into the resultant reaction productto cause sedimentation and precipitation of the copolymer, and theprecipitate was filtered off and vacuum-dried to obtain a coating resin1.

A total of 30 parts of the coating resin 1 thus obtained was dissolvedin 40 parts of toluene and 30 parts of methyl ethyl ketone to obtain apolymer solution 1 (amount of solids was 30% by mass).

<Preparation of Coating Resin Solution 1>

Polymer solution 1 (concentration of resin 33.3% by mass, solids 30%)toluene 66.4% by mass, and carbon black (Regal 330; manufactured by 0.3%by mass Cabot Corporation)(primary particle diameter 25 nm, nitrogen adsorption specific surfacearea 94 m²/g, and DBP oil absorption amount 75 mL/100 g)were dispersed for 1 hours with a paint shaker using zirconia beadshaving a diameter of 0.5 mm. The obtained dispersion was filtered with a5.0 μm membrane filter to obtain a coating resin solution 1.

Production Example of Magnetic Carrier 1

(Resin Coating Step):

The coating resin solution 1 was loaded into a vacuum degassing typekneader maintained at room temperature in an amount of 2.5 parts as aresin component with respect to 100 parts of the magnetic coreparticles 1. After loading, the mixture was stirred for 15 minutes at arotation speed of 30 rpm. After the solvent was volatilized to at leasta certain level (80% by mass), the temperature was raised to 80° C.while mixing under reduced pressure, and toluene was distilled off over2 hours, followed by cooling.

The obtained magnetic carrier was classified to cut the products with alow magnetic force by magnetic separation, passed through a sieve havingan opening of 70 μm, and classified with an air classifier to obtain amagnetic carrier 1 with a 50% particle diameter (D50), based on a volumedistribution standard, of 38.2 μm.

The toners 1 to 34 were added to the magnetic carrier 1 so that thetoner concentration became 8.0% by mass, and the components were mixedusing a V type mixer (V-10 type: Tokuju Corporation) under theconditions of 0.5 s⁻¹ and a rotation time of 5 minutes to obtaintwo-component developers 1 to 34.

Examples 1 to 28 and Comparative Examples 1 to 5

Evaluation was carried out using the two-component developers 1 to 33.

A Canon printer imageRUNNER ADVANCE C5051 for digital commercialprinting was used as an image forming apparatus and was modified so thatthe fixing temperature and process speed could be freely set. Atwo-component type developer was placed in the developing device at thecyan position of this modified machine, and the DC voltage V_(DC) of thedeveloper carrying member, the charging voltage V_(D) of theelectrostatic latent image bearing member, and the laser power wereadjusted to obtain the desired amount of the toner on the electrostaticlatent image bearing member or paper, and the below-describedevaluations were carried out. The results are shown in Table 3.

<Evaluation 1: Tinting Strength>

The printing speed of the image forming apparatus was made 1.5 times thenormal printing speed (A4 lateral feed 76.5 prints/min).

The evaluation environment was set to normal temperature and normalhumidity (23° C., 50% RH), and paper CS-814 for copiers (A4, basisweight 81.4 g/m², marketed by Canon Marketing Japan Inc.) was used asevaluation paper.

The relationship between the image density and the amount of appliedtoner on the paper was examined by changing the toner loading amount onthe paper in the evaluation environment.

Next, the image density of an FFH image (solid portion) was adjusted to1.55, and the amount of applied toner when the image density became 1.55was determined.

The FFH image refers to a value obtained by representing 256 tone levelsin a hexadecimal notation, and is such an image that 00H represents thefirst tone level (white portion) and FFH represents the 256-th tonelevel (solid portion).

The image density was measured using an X-Rite color reflectiondensitometer (500 series: manufactured by X-Rite Incorporated).

The tinting strength of the toner was evaluated from the applied toneramount (mg/cm²) according to the following criteria. When the evaluationwas A to C, it was determined that the effect of the present inventionwas obtained.

(Evaluation Criteria)

A: less than 0.45,

B: at least 0.45 and less than 0.55,

C: at least 0.55 and less than 0.65,

D: at least 0.65.

<Evaluation 2: Hot Offset Resistance>

Paper: CS-680 (68.0 g/m²)

(marketed by Canon Marketing Japan Inc.)

Applied toner amount: 0.08 mg/cm²

Evaluation image: an image of 10 cm² placed at both ends of the paper

Fixing test environment: normal-temperature low-humidity environment,temperature 23° C./humidity 5% RH (hereinafter “N/L”)

The process speed of the image forming apparatus was set at 450 mm/secand the fixing temperature was increased by 5° C. from 150° C. toevaluate hot offset resistance.

The evaluation procedure involved passing 10 plain postcards at thecenter position of the fixing belt of the fixing device of the imageforming apparatus and then outputting the fixed image under theabovementioned conditions.

The fogging value of the fixed image was used as an evaluation index ofhot offset resistance.

Fogging was calculated by measuring an average reflectance Dr (%) of theevaluation paper before image formation and a reflectance Ds (%) of awhite background portion after the fixing test with a reflectometer(“REFLECTOMETER MODEL TC-6DS” manufactured by Tokyo Denshoku Co., Ltd.)and using the following equation. The fogging thus obtained wasevaluated according to the following evaluation criteria. When theevaluation was A to C, it was determined that the effect of the presentinvention was obtained.Fogging (%)=Dr(%)−Ds(%)(Evaluation Criteria)A: less than 0.2%,B: at least 0.2% and less than 0.5%,C: at least 0.5% and less than 1.0%,D: at least 1.0%.

<Evaluation 3: Charging Performance Under High-Temperature andHigh-Humidity Environment>

The toner on the electrostatic latent image bearing member was sucked inand collected by using a metal cylindrical tube and a cylindrical filterto calculate the triboelectric charge quantity and the applied toneramount of the toner.

Specifically, the triboelectric charge quantity and the applied toneramount on the electrostatic latent image bearing member were measuredwith a Faraday cage.

The Faraday cage, as referred to herein, is a coaxial double cylinder inwhich the inner cylinder and the outer cylinder are insulated from eachother. Where a charged body with a charge amount Q is inserted in theinner cylinder, it is as if a metal cylinder with a charge amount Q ispresent due to electrostatic induction. The induced charge amount wasmeasured with an electrometer (KEITHLEY 6517A, manufactured by KeithleyInstruments Inc.), and the ratio (Q/M) obtained by dividing the chargeamount Q (mC) by the mass M (kg) of the toner in the inner cylinder wastaken as the triboelectric charge quantity of the toner.

Further, the suction area S was measured and the applied toner amountper unit area was obtained by dividing the toner mass M by the suctionarea S (cm²).

The rotation of the electrostatic latent image bearing member wasstopped before the toner layer formed on the electrostatic latent imagebearing member was transferred to the intermediate transfer member, andthe toner image on the electrostatic latent image bearing member wasdirectly measured by air suction.Applied toner amount (mg/cm²)=M/STriboelectric charge quantity of the toner (mC/kg)=Q/M

The applied toner amount on the electrostatic latent image bearingmember under a high-temperature and high-humidity environment (32.5° C.,80% RH) in the image forming apparatus was adjusted to 0.35 mg/cm², andthe toner was collected by suction with the metal cylindrical tube andcylindrical filter. In this case, the charge amount Q accumulated at thecapacitor through the metal cylindrical tube and the mass M of thecollected toner were measured and the charge amount Q/M (mC/kg) per unitmass was calculated and taken as the charge amount Q/M (mC/kg) per unitmass on the electrostatic latent image bearing member. When theevaluation based on the following evaluation criteria was A to C, it wasdetermined that the effect of the present invention was obtained.

(Evaluation Criteria)

A: Q/M is at least 36.0 mC/kg.

B: Q/M is at least 33.0 mC/kg and less than 36.0 mC/kg.

C: Q/M is at least 30.0 mC/kg and less than 33.0 mC/kg.

D: Q/M is less than 30.0 mC/kg.

<Evaluation 4: Charge Retention Property Under High-Temperature andHigh-Humidity Environment>

After evaluating the charging performance, the developing device wasremoved from the apparatus and allowed to stand for 72 hours under ahigh-temperature and high-humidity environment (32.5° C., 80% RH). Thedeveloping device was then again mounted on the apparatus, and thecharge amount Q/M per unit mass on the electrostatic latent imagebearing member was measured with the same DC voltage V_(DC) as was usedin the evaluation of charging performance.

The Q/M per unit mass on the electrostatic latent image bearing memberin the evaluation of charging performance was taken as 100%, and theretention ratio of the charge amount Q/M per unit mass on theelectrostatic latent image bearing member after the device was allowedto stand for 72 hours ([(Q/M of evaluation after the device was allowedto stand)/(Q/M of evaluation of charging performance)]×100) wascalculated and determined according to the following criteria. When theevaluation was A to C, it was determined that the effect of the presentinvention was obtained.

(Evaluation Criteria)

A: Retention ratio is at least 90%.

B: Retention ratio is at least 85% and less than 90%.

C: Retention ratio is at least 80% and less than 85%.

D: Retention ratio is less than 80%.

<Evaluation 5: Low-Temperature Fixability>

Paper: CS-680 (68.0 g/m²)

(marketed by Canon Marketing Japan Inc.)

Applied toner amount: 1.20 mg/cm²

Evaluation image: an image of 10 cm² arranged at the center of the paper

Fixing test environment: low-temperature low-humidity environment, 15°C./10% RH (hereinafter “L/L”)

The DC voltage V_(DC) of the developer carrying member, the chargingvoltage V_(D) of the electrostatic latent image bearing member, and thelaser power were adjusted to obtain the abovementioned amount of thetoner on the paper, the process speed was then set to 450 mm/sec, thefixing temperature was set at 130° C., and low-temperature fixabilitywas evaluated.

The value of an image density reduction ratio was used as an evaluationindex of the low-temperature fixability.

To determine the image density reduction ratio, first, the density ofthe fixed image in the center portion was measured using an X-Rite colorreflection densitometer (500 series: manufactured by X-RiteIncorporated). Next, the fixed image was rubbed (5 times in areciprocating manner) with Silbon paper by applying a load of 4.9 kPa(50 g/cm²) to the portion where the density of the fixed image wasmeasured, and the density of the fixed image was measured again. Then,the reduction ratio (%) of the density of the fixed image before andafter rubbing was measured. When the evaluation based on the followingevaluation criteria was A to C, it was determined that the effect of thepresent invention was obtained.

(Evaluation Criteria)

A: density reduction ratio is less than 1.5%.

B: density reduction ratio is at least 1.5% and less than 2.0%.

C: density reduction ratio is at least 2.0% and less than 3.0%.

D: density reduction ratio is at least 3.0%.

<Evaluation 6: Blocking Resistance>

A total of 5 g of toner was placed in a 100 mL plastic container andallowed to stand for 48 hours in a thermostat with variable temperatureand humidity (settings: 55° C., 41% RH). Then, agglomeration property ofthe toner was evaluated.

The agglomeration property was evaluated by using the residual ratio ofthe remaining toner as an evaluation criterion when sieving for 10seconds with a powder tester PT-X manufactured by Hosokawa MicronCorporation at an amplitude of 0.5 mm with a mesh opening of 20 μm. Whenthe evaluation was A to C, it was determined that the effect of thepresent invention was obtained.

(Evaluation Criteria)

A: residual ratio is less than 2.0%.

B: residual ratio is at least 2.0% and less than 10.0%.

C: residual ratio is at least 10.0% and less than 15.0%.

D: residual ratio is at least 15.0%.

TABLE 3 Evaluation 2 Evaluation 4 Evaluation 5 Evaluation 1 HotEvaluation 3 Charge Low Evaluation 6 Toner Tinting offset Chargingretention temp. Blocking No. Rank strength Rank resistance Rankperformance Rank property Rank fixability Rank resistance Example 1 1 A0.20 A 0.0 A 40.0 A 98 A 0.3 A 0.2 Example 2 2 A 0.23 B 0.3 A 39.5 A 98A 0.5 B 2.6 Example 3 3 A 0.23 A 0.0 A 39.5 A 97 B 1.6 A 0.8 Example 4 4A 0.24 A 0.1 B 35.5 A 97 A 0.5 B 2.6 Example 5 5 A 0.27 B 0.3 A 38.5 A96 A 0.4 A 0.6 Example 6 6 A 0.24 A 0.0 A 38.5 A 97 B 1.7 A 0.8 Example7 7 A 0.30 A 0.0 A 38.0 A 96 B 1.8 A 0.8 Example 8 8 A 0.32 A 0.1 A 38.5A 92 C 2.3 A 1.0 Example 9 9 A 0.30 B 0.3 A 38.0 A 95 A 0.9 B 3.4Example 10 10 B 0.47 A 0.1 A 38.0 A 94 B 1.7 A 1.0 Example 11 11 A 0.31A 0.1 A 37.5 B 87 A 0.5 B 4.6 Example 12 12 C 0.56 B 0.3 A 38.0 A 95 A0.8 A 0.8 Example 13 13 A 0.31 B 0.4 A 37.5 A 94 A 0.9 A 1.0 Example 1414 C 0.59 A 0.1 A 37.5 A 96 A 1.0 A 1.4 Example 15 15 A 0.31 A 0.1 B35.5 C 82 A 0.8 C 11.2 Example 16 16 A 0.32 A 0.1 A 37.5 A 94 C 2.6 A1.6 Example 17 17 A 0.27 C 0.5 A 36.5 A 95 A 1.1 C 12.8 Example 18 18 A0.25 A 0.1 A 37.0 A 91 C 2.5 A 1.6 Example 19 19 A 0.31 A 0.1 C 32.5 A93 A 0.6 C 13.8 Example 20 20 A 0.36 C 0.6 A 36.5 A 96 A 0.8 A 1.2Example 21 21 A 0.41 C 0.6 A 37.0 A 93 A 0.9 B 5.6 Example 22 22 A 0.39A 0.1 B 35.5 B 87 A 1.0 B 5.8 Example 23 23 A 0.38 A 0.1 B 34.0 B 86 A0.7 B 5.6 Example 24 24 A 0.29 A 0.1 C 32.5 C 82 A 0.9 B 6.8 Example 2525 A 0.32 A 0.1 C 31.5 C 81 A 1.0 B 7.0 Example 26 26 A 0.42 A 0.1 A36.5 A 93 C 2.5 B 7.8 Example 27 27 A 0.32 A 0.1 A 37.0 C 83 A 1.1 B 8.0Example 28 28 C 0.58 C 0.8 A 36.5 A 93 A 1.2 C 14.2 Comparative 29 A0.32 A 0.1 D 29.0 D 78 D 3.1 D 15.8 example 1 Comparative 30 C 0.59 D1.4 D 28.5 D 77 D 3.2 C 14.6 example 2 Comparative 31 D 0.68 D 1.6 D29.0 D 78 D 3.4 D 15.8 example 3 Comparative 32 D 0.67 D 1.7 D 28.0 D 75D 3.2 D 16.6 example 4 Comparative 33 D 0.75 D 1.8 D 26.5 D 68 D 3.8 D18.4 example 5

A polymer 19 used in a toner 29 of Comparative Example 1 did not containa monomer unit derived from cycloalkyl (meth)acrylate, and thelow-temperature fixability, charging performance, charge retentionproperty, and blocking resistance were in unacceptable ranges.

A polymer 20 used in a toner 30 of Comparative Example 2 had no monomerunit derived from α-methylstyrene. As a result, the softening point ofthe polymer was high, the relationship −18≤[Tk−Tm]≤10 was not satisfied,wax dispersibility decreased, and the low-temperature fixability, hotoffset resistance, charging performance, and charge retention propertywere in unacceptable ranges.

A toner 31 of Comparative Example 3 used a polymer 21 and thetemperature of the kneaded product during kneading was 95° C. In thiscase, the relationship −18≤[Tk−Tm]≤10 was not satisfied, and the tintingstrength, low-temperature fixability, hot offset resistance, blockingresistance, charging performance, and charge retention property were inunacceptable ranges.

When a toner 32 of Comparative Example 4 was produced, the relationship−18≤[Tk−Tm]≤10 was not satisfied, and the tinting strength,low-temperature fixability, hot offset resistance, blocking resistance,charging performance, and charge retention property were in unacceptableranges.

When a toner 33 of Comparative Example 5 was produced, the relationship−18≤[Tk−Tm]≤10 was not satisfied, and the tinting strength, hot offsetresistance, blocking resistance, low-temperature fixability, chargingperformance, and charge retention property were in unacceptable ranges.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2016-159640, filed, Aug. 16, 2016, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A toner production method comprising: amelt-kneading step of melt-kneading a resin composition including abinder resin, a colorant, a wax, and a wax dispersant to obtain amelt-kneaded product; and a pulverizing step of pulverizing themelt-kneaded product, wherein −18≤[Tk−Tm]≤10 where a temperature of themelt-kneaded product at an end of the melt-kneading step is Tk (° C.),and a softening point of the wax dispersant is Tm (° C.), the waxdispersant is a polymer in which a styrene acrylic polymer is grafted toa polyolefin, the styrene acrylic polymer has a monomer unit derivedfrom α-methylstyrene and a monomer unit derived from a cycloalkyl(meth)acrylate, the monomer unit derived from the cycloalkyl(meth)acrylate is represented by formula (2)

where R₁ represents a hydrogen atom or a methyl group, and R₂ representsa cycloalkyl group, and the monomer unit derived from α-methylstyrene isrepresented by formula (4)


2. The toner production method according to claim 1, wherein an amountof the monomer unit derived from α-methylstyrene in the polymer is 5.0to 30.0% by mass.
 3. The toner production method according to claim 1,wherein the softening point of the wax dispersant is 100.0 to 130.0° C.4. The toner production method according to claim 1, wherein the styreneacrylic polymer further has a monomer unit represented by formula (3)

where R₃ represents a hydrogen atom or a methyl group, and n representsan integer of 1 to
 18. 5. The toner production method according to claim1, wherein the monomer unit derived from the cycloalkyl (meth)acrylateis derived from cyclohexyl methacrylate.
 6. The toner production methodaccording to claim 1, wherein the polyolefin is polypropylene having amelting point of 70 to 90° C.
 7. The toner production method accordingto claim 1, wherein the amount of the polymer is 1.0 to 10.0 parts bymass with respect to 100 parts by mass of the binder resin.